Academics and Research / Magazine Feature

Stencel says new status of Pluto is a step up in the world

DU Astronomy Professor Robert Stencel had a hand in making your “Planets of the Solar System” poster obsolete. 

In August, Stencel presented his observations of an interacting binary star system at the International Astronomical Union meeting in Prague; but the big news to come out of the gathering was the vote to reclassify Pluto as a dwarf planet. 

“I believe it’s actually a promotion for Pluto, because it highlights it as the leading member of a new category, instead of a tiny, moon-size maverick that doesn’t move like the other planets,” Stencel says. 

Although the astronomical union has been discussing Pluto’s status for the past six years, the need for a decision was becoming urgent because astronomers keep finding planet-like objects — some larger than Pluto — on the fringes of the solar system. 

Stencel voted for the change. 

“If you look at astronomy textbooks, there are the terrestrial, earth-like planets (Mercury, Mars, Earth and Venus), there are the giant planets (Jupiter, Saturn, Uranus and Neptune), and then there’s ‘other,’ and Pluto has been stuck in with ‘other’ for 20-some years,” he says.

“Instructors have had to be a little bit apologetic: What is Pluto? Why isn’t it in one of these proper categories?” 

But not everyone is happy about the decision. Meg Spohn, a DU doctoral candidate in international studies, signed a Web-based petition imploring the union to reconsider. Among other reasons, the petition takes issue with using dynamics (location) rather than intrinsic characteristics to define an object. 

“Even though I’m not a professional astronomer, things astronomical interest me,” Spohn wrote in her blog “The reclassification of Pluto annoyed me on a few different levels: logically, politically and otherwise.” 

Stencel describes the new framework of terrestrials, giants, dwarf planets and other bodies as a seismic conceptual step about the nature of the solar system that recognizes that separate physical processes created the different types of objects. 

“The cake has been baked, and we see the result,” he says. “Now we’re trying to find out what ingredients and how much cooking time has gone into the recipe.”

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